Shared DNA switch turns on genes in both bacteria and yeast

Scientists have discovered genes associated with chemosynthesis in bacteria residing in the gills of coral reef fish. Until now, such bacteria were primarily found in environments like deep-sea vents or in association with invertebrates. The study, published in PLOS Genetics, reveals that the gill microbiome of the hamlet fish (Hypoplectrus spp.) is complex and specialized, potentially playing a role in the fish's metabolism, immunity, and health.

The researchers sequenced the metagenome of gill samples from hundreds of hamlets across the Greater Caribbean, finding that over 95% of the DNA in the gills originated from the fish itself, with only a small fraction being microbial DNA. Among the 70 bacterial genomes they reconstructed, the majority were new to science, with particular significance being that the most common bacteria possess genes necessary for chemosynthesis—the ability to convert carbon dioxide into energy using inorganic compounds, rather than relying on sunlight.

While similar bacteria have been found in deep-sea environments and on other marine organisms, this is the first documented presence of chemosynthetic bacteria in fish gills. The discovery opens new avenues of research into the role of gill microbiome in fish physiology and health, particularly in the context of aquaculture and natural populations facing environmental changes.